The comparative ecology of six marine ecosystems

Abstract

We compare six marine ecosystems worldwide, using a network analysis of carbon flows for the Swartkops and Ems estuaries, Chesapeake Bay, the Baltic Sea and the Peruvian and Benguela upwelling regions. We find that there is an inverse correlation between the Finn Cycling Index (FCI) and the normalized internal ascendancy or system maturity ( A i : C i ). We also show that there is a clear distinction between system maturity ( A i : C i ) and the production: biomass ( P :B ) ratio; in upwelling systems the P:B and A i : C i ratios are both high, whereas in estuarine systems the ratio is low. The P:B ratio thus cannot be used as an indicator of marine ecosystem evolution. Contrary to current views on ecosystems, the aggregate amount of cycling of materials, such as carbon, is not seen as an indication of system maturity but rather of stress. The reason that higher stressed systems are associated with a higher throughput or FCI could be because perturbations frequently impact higher-level species to a greater extent than the lower trophic components. Any release of standing biomass from these higher levels could therefore be taken up through increased recycling via short intense loops. Overall, we conclude that a network representation is a suitable methodology for inter-ecosystem comparisons.